It's no secret that Chevrolet has been around for a very long time. And in that time, they've learned a thing or two about making some power. Since Chevrolet first invented the small-block, they've also been working on ways to improve it. We thought it was time we tried some of their parts on our little mule. After a brief phone conversation with the technicians at GM Performance Parts and the folks at Scoggin-Dickey Performance Center, we were convinced that Danger Mouse had to wear a set of GM's Aluminum Fast Burn cylinder heads for its next dyno dual.
FAST BURN TECH
If you're not familiar with the Fast Burn heads, here's some info. They're designed to fit any '58-00 283-400-cid small-blocks using a conventional water flow design, so that means the LT1 and LT4 are out. Of course, they won't fit LS1 either, because it's a completely different animal altogether. The Fast Burn heads are a 23-degree wedge design developed using the best of GM Motorsports and GM Production cylinder head techniques. The heads can fit either self-aligning rocker arms, as we chose to run, or standard rockers and guide plates. They're also dual drilled to accept either the late model "Vortec"-style intake manifold that uses only eight bolts to mount it to the head, or they'll accept a raised-port, 23-degree intake. The valve cover rails are also dual drilled to accept the late-style center-bolt valve covers or the early perimeter bolt-style covers.
The name "Fast Burn" refers to its combustion chamber's ability to quickly and completely burn the air/fuel mixture. The chamber shape is designed to work best with flattop pistons and GM does not recommend that you try to re-shape the chamber for more power. This new head is also manufactured with a .400-inch thick deck, which creates considerable gasket clamping force and strength.GM claims that this head is an "out-of-the-box" design that does not require any additional porting for maximum performance. Although, according to GM, polishing the chambers and exhaust ports is acceptable and may increase power, but we left them stock.
The Fast Burn heads feature a raised intake port that measures 210cc. Normally, we'd say that 210cc is kinda big for the street, but GMPP did their homework on this head and combined it with smaller than normal valves (2.00 intake, 1.55 exhaust) and an efficient 62cc chamber. The hollow-stem intake valves and sodium-filled exhaust valves are incorporated to reduce mass which allows for better valve control at higher rpm. We ordered our heads as a complete set with GMPP LT4/ZZ4 springs (101 pounds at 1.78 inches, 332 pounds at 1.22 inches) with lightweight LT4/ZZ4 retainers, and 3/8-inch screw-in studs.
GM told us that the Fast Burn heads would respond well to a fair amount of valve lift, but we didn't want to go too radical with the cam. We chose a healthy COMP Cams Xtreme Energy hydraulic roller grind for this test. The cam's 230/236 duration at .050 meant that it would idle acceptably on the street, but would still have a notable tone. GMPP 1.5:1 aluminum roller rocker arms with self-aligning tips were employed to keep valve lift in the cam's advertised .510/.520-inch range. Since Danger Mouse is equipped with a belt drive, we tested several different intake centerline installed positions before we came up with the best results, which turned out to be advanced 2 degrees (104 intake CL).
This month's dyno test did not involve any direct comparison to any previous tests. We tested DM as if it were an entirely new motor this month. We did, however, reuse several of our original key pieces, like the Demon 750 vacuum secondary carb, MSD billet distributor and wires, and of course, the same short-block as in all the other tests. The results shown here are listed chronologically as test 26 just in case we want to refer back to them at a later date.
Danger Mouse specs for Test 13:
355 cid, 9.4:1 cr, 4.030-bore four-bolt Motown block, 3.48-stroke Lunati crank, 5.7-inch Lunati rods
Test 26: GMPP Aluminum Fast Burn heads (62cc chambers, 210cc runners, 2-inch hollow stem intake valves, 1.55-inch sodium filled exhaust valves), GMPP single-plane intake manifold, Demon 750 carb, COMP Cams Xtreme Energy hydraulic roller camshaft XR-282-HR (230/236 at .050, 282/288 adv, .510/.520 lift, 110 LS). GMPP 1.5:1 aluminum roller rockers, 36 degrees total advance.
The first pulls on Westech's Superflow 901 dyno were promising. Interestingly, after an entire day of testing and tuning, trying different carb spacers, cam and ignition timing, and carb jetting, it turned out that our first set-up was practically the best. The only change the engine responded well to was advancing the cam. Everything else we tried cost us a little power. Which made it very clear to us that this was a very well matched package. It's pretty cool to know that these few GMPP/COMP Cams/Demon parts can make a truly bolt-on, 450-plus hp small-block that can run all day on 91-octane and still treat you like the royalty you'll become from stoplight to stoplight.